Air flow control structure for web driers

ABSTRACT

A web drier construction comprising a housing having inlet and outlet openings and means for teansporting a web through the housing between said openings. Air nozzles are positioned for applying air to the web so that ink or other material on the web will be dried during movement of the web through the housing. A conduit structure feeds air to the nozzles, and an exhaust means is connected to the housing for withdrawing air from within the housing. The nozzles which are positioned adjacent the inlet and outlet openings carry extensions having air discharge openings which operate to produce air flow transversely relative to the web movement. This air flow operates to disrupt the longitudinal air streams which flow from the nozzles toward the inlet and outlet openings. The extensions, therefore, assist in eliminating the discharge of air from the housing into the atmosphere surrounding the housing.

United States Patent Capizzi 51 May 16, 1972 [54] AIR FLOW CONTROL STRUCTURE Primary Examiner-Carroll B. Dority, Jr.

FOR WEB DRIERS AttorneyMcDougall, Hersh & Scott [72] Inventor: Victor T. Capizzi, Chicago, Ill. [57] ABSTRACT [73] Asslgnee: & -r Chicagov A web drier construction comprising a housing having inlet [22] Filed: 30 1970 and outlet openings and means for teansporting a web through the housing between said openings. Air nozzles are positioned PP 102,760 for applying air to the web so that ink or other material on the web will be dried during movement of the web through the 52 us. Cl ..34/156 34/160 A cmiduit Structure feeds air the 9 [5 1 Int. Cl ..F26b 13/00 exhaust. l ls conilected to the houslqg for wlthqhawmg air 58 Field of Search ..34 155 156 160 fmm the musmg' The "wigs jacent the inlet and outlet openings carry extensions having air [56] References Cited discharge openings which operate to produce air flow transversely relative to the web movement. This air flow operates UNlTED STATES PATENTS to disrupt the longitudinal air streams which flow from the nozzles toward the inlet and outlet openings. The extensions, 2,384,990 9/1945 French ..34/ 160 th f assist in eliminating the discharge f air f the 2,700,226 955 Dunglerm housing into the atmosphere surrounding the housing. 3,559,301 2/1971 Fraser ..34/l56 7 Claims, 7 Drawing Figures 10 /28 26 23) K V /f/ AIR FLOW CONTROL STRUCTURE FOR WEB DRIERS This invention relates to improvements in web drier constructions. The invention is particularly concerned with drier constructions of the type used for handling webs upon movement of the webs from printing apparatus. Thus, the webs, at this point, carry wet ink, and web drier constructions are utilized for removing the ink solvents whereby a dry or substantially dry web will exit from the drier construction.

The use of hot air for purposes of drying printed webs has become prevalent. In such constructions, for example as described in I-lering, et al. U.S. Pat. No. 3,319,354, a plurality of air discharge nozzles are located within a drier housing. These discharge nozzles extend transversely relative to the direction of air movement, and conduits supply air to the nozzles whereby air streams are continuously directed onto the web surfaces.

Air exhaust means are associated with the housing for pur poses of withdrawing the air discharged from the nozzles. These air exhaust means also operate to remove the solvent which has evaporated during drying of the ink. In addition, air from the atmosphere surrounding the drier is drawn into the housing at least through the web inlet and outlet openings and, therefore, this air must also be removed by the exhaust means.

Since the air discharged from the nozzles must be heated to provide efficient drying, it is desirable to recirculate at least portions of the air exhausted from the housing. Recirculation is limited, however, by the solvent content of the air. Thus, all of the air cannot be recirculated since the solvent content would then build up to the point of saturation whereby condensation would occur to an undesirable degree, whereby the drying efficiency of the air would be seriously diminished, and thereby leading to contamination which would create maintenance problems.

Since some of the exhausted air is not recirculated, this air must be discharged from the system. Since the air contains solvent, however, anti-pollution treatment of the air is necessary before it is passed into the atmosphere. Since the anti-pollution treatment is expensive, it is desirable to minimize the volume of air which must be passed through such equipment.

It is a general object of this invention to provide an improved structure for air nozzles employed in web drier constructions whereby the operation of the constructions can be improved from the standpoint of the burden placed on exhaust means and pollution control means.

It is a more specific object of this invention to provide an improved nozzle construction which will serve to minimize the volume of air handled by the web drier exhaust means by minimizing the volume of air drawn in to the drier from the surrounding atmosphere.

These and other objects of this invention will appear hereinafter and for purposes of illustration, but not of limitation, specific embodiments of the invention are shown in the accompanying drawings in which FIG. I is a longitudinal, schematic sectional view of a web drier construction characterized by the features of this invention;

FIG. 2 is an enlarged fragmentary sectional view taken about the line 22 ofFIG. 1;

FIG. 3 is an enlarged fragmentary sectional view, taken about the line 33 of FIG. 1;

FIG. 4 is a horizontal sectional view of a drier construction characterized by the features of this invention;

FIG. 5 is an enlarged fragmentary sectional view taken about the line 55 of FIG. 4;

FIG. 6 is a horizontal sectional view of the portion of the drier construction shown in FIG. 5; and,

FIG. 7 is a vertical sectional view taken about the line 77 of FIG. 5.

The web drier construction of this invention comprises a housing defining inlet and outlet openings, and means for transporting a web through the housing. Air nozzle structures are positioned for discharging streams of air into contact with the moving web. A conduit structure feeds air to these nozzles, and the air is discharged through the noules into contact with the web. An exhaust system is connected to the housing for withdrawing air including air mixed with solvent, and including the air which is drawn into the housing from the surrounding atmosphere through the inlet and outlet openings which are provided for the web.

The specific improvements of the invention relate to the design of the nozzles, particularly the nozzles located adjacent the inlet and outlet openings. These nozzles are provided with extensions defining air discharge openings whereby streams of air can be applied by the extensions to the web. These air streams develop at least some flow which is transverse to the direction of web movement. This flow tends to disrupt the flow of air longitudinally in the direction of air movement. It has been found that by employing noule extensions functioning in this manner, the tendency for air to move out of the drier construction is reduced. By reducing this tendency, the demand on the exhaust means for the construction is reduced. There is also a reduction in the inflow of atmospheric air through the inlet and outlet openings.

This latter benefit occurs because the negative pressure produced by the exhaust means is reduced when compared with a system which does not utilize the improvements of the invention. Furthermore, in some systems, the flow of atmospheric air is considered necessary since this in-flow serves as an air curtain to block the discharge of air from the construction to the atmosphere. The improvement of this invention minimizes the necessity for a substantial air curtain which, therefore, reduces the burden on the exhaust means of the construction.

FIG. I of the drawings illustrates a web drier construction 10 including a surrounding housing 12. This housing defines an inlet opening 14, to permit entry ofa web 16. The web is transported through the housing and then out through the out let opening 18. The invention will be described with reference to web driers of the type depending upon air streams for purposes of supporting the web during movement through the drier. Thus, the force of the air which is discharged from the nozzles as well as the location of the nozzles is maintained so that the web will not come into contact with the nozzles. This would, of course, damage the printed web, and air drier constructions are quite effective in avoiding such damage.

The air nozzles 20 are located in spaced apart relationship within the drier. Each of these nozzles includes a centrally located plate 22 which defines outlet openings 24 on either side. This provides for the discharge from each nozzle of a pair of long narrow streams transversely across the web.

In the embodiments illustrated, the nozzles 20 on one side of the web are staggered relative to the nozzles on the opposite side of the web. This leads to the formation of waves in the web as it moves through the construction. Each of the nozzles is connected to an air input manifold 25 with each manifold being connected to an air input conduit 26. The conduits may then be connected to a common air supply.

Air discharge openings 28 are located at each end of the construction above and below the web. Each of these discharge openings is preferably connected to a common exhaust conduit which includes means for directing a portion of the air for recirculation, and a separate portion of the air to anti-pollution equipment. With the arrangement described,

the air discharged from the nozzles will be mixed with air entering the drier through the inlet and outlet openings 14 and 18. This air mixture along with the evaporated solvents will then pass out through the exhaust openings 28.

Under normal circumstances, the air discharged from the nozzles tends to move longitudinally after contact with the web surfaces. In the absence of a significant air flow through the inlet and outlet openings 14 and 18, portions of the longitudinally flowing air streams will discharge through these openings thereby contaminating the surrounding atmosphere. Since this is an intolerable situation, a significant inflow of air through the openings 14 and 18 has been required. As noted, this increases the demand on the power requirements for the exhaust structures, and also increases demands on the air pollution equipment. This latter equipment usually requires heating, and any increase in volume will require a corresponding increase in energy for heating purposes even though the volume of pollutants is not any greater.

The problems associated with present equipment are significantly reduced by the modification of the air discharge nozzles in accordance with the concepts of this invention. Specifically, these air discharge nozzles are provided with extensions such as those shown at 30 in FIGS. 2 and 3. These extensions comprise triangularly shaped portions formed as continuations of the outer walls 32 of the manifold structures 25. Triangularly shaped plates 34 are positioned within these extensions, and these plates are located in spaced relationship relative to the extensions for forming air discharge openings 36 around the periphery of the plates. The plates may be secured to the extensions by means of centrally located, vertically extending rods such as shown at 38 in FIG. 1, or the plates may be welded to the extensions at selected points as shown at 40 in FIG. 3.

As best shown in FIG. 3, the streams issuing from the openings 36 tend to flow transversely relative to the direction of web movement. In practice, the air streams issuing from these openings will be directed vertically downwardly and then spread out transversely after contact with the web creating turbulence tending to lift the air from the web surface.

The transverse flow provided by the nozzle extensions will disrupt the air flow from the nozzles 30. This disruption will substantially reduce any tendency toward passage of air outwardly through openings 14 and 18. By creating turbulence or disturbance in the longitudinally flowing streams, the air is lifted or separated from the web surfaces and the tendency for these streams to be exhausted through the openings 28 is, therefore, greatly increased. This will, of course, greatly reduce the possibility of contamination of the atmosphere surrounding the drier. Furthermore, the power required for exhausting the air will be reduced since the air from the nozzles can be more easily withdrawn because of the turbulance created by the nozzle extensions.

FIGS. 4 through 7 illustrate a drier construction 50 which incorporates the improved features of this invention. This drier construction includes a surrounding housing 52 having upper and lower openings for communication with air inlet conduits 54. The inlet conduits deliver air to manifold structures 56 which, in turn, feed nozzles 58. The air which passes from the nozzles 58 engages the web 60 and is then exhausted through the exhaust openings 62 which communicate with exhaust conduits 64. As best shown in FIGS. 5, 6 and 7, a baffle 66 is movable positioned in line with the exhaust opening 62 for purposes of regulating the air flow in the exhaust. Each baffle is mounted on a rod 68 controlled by handle 70. The exhaust conduits 64 also communicate with additional openings 72 which are separated from the opening 62 by means of a wall 74. This wall 74 comprises an extension of the front wall 76 of the manifold structure 56. This arrangement provides a passage between the front wall 76 and the wall 78 of the housing 52 whereby air drawn in through the housing opening 80 will move upwardly between these walls and to the opening 72. A baffle 82 having an adjusting handle 84 is located between the walls 76 and 78 for controlling the air flow between the inlet opening and the exhaust opening 72.

The foremost nozzle 86 is provided with an extension 88 of the type previously described. It will be noted that the position of the nozzle and the extension provides for the free flow of air to the exhaust passage 72 as regulated by the baffle 82. The provision of the extensions 88 in a construction of the type shown in FIGS. 4 through 7 results in a distinct improvement in operating efficiency. In the absence of the extensions, it has been found necessary to draw an extensive amount of air through the openings in the housing for passage to the exhaust opening 72. This air provided an effective curtain forpreventing discharge of air contaminated with solvent. The arrangement was undesirable, however, because of the increased power requirement and increased burden on the anti-pollution equipment. When the extensions 88 are employed, the air curtain requirements was substantially reduced providing the advantages described above.

The nozzle extensions may be associated with only the nozzles which are located close to the housing inlet and outlet openings. Thus, by disrupting the longitudinal air flow at the extreme ends of the construction, a distinct improvement in efficiency is realized. In the embodiment shown in FIG. 1 where the nozzles are staggered, the extensions may be effectively associated with only the left-hand nozzle of the top set and the right-hand noule of the lower set. This arrangement is satisfactory since the curvature in the web tends to disrupt the air flow from the end nozzles at the lower left and upper right of FIG. 1 to the extent that only the extreme nozzles on the other side create the problems described.

The nozzle extensions are preferably dimensioned so that their combined length will at least be about equal to the length of the nozzles. The extensions should also be relatively long since if the openings 36 extend for a substantial distance, there is a greater possibility of providing sufficient transverse air flow to secure the necessary disruption of the longitudinal air flow. In this connection, the configuration of the nozzle extensions may vary considerably as long as the transverse air flow is obtained. Extensions having single slots extending at a 90 angle relative to the noules are contemplated as is the use of any design which will create transversely directed streams rather than streams directed totally vertically downwardly or upwardly. Appropriate baffles may thus be employed to direct at least portions of streams at an angle.

The number of extensions may vary, depending upon the particular drier operation. A greater number of extensions will be required in the case of very high speed operations so that transverse flow can build up fast enough to disrupt the longitudinal flow. In practice, and in order to have a combined extension length equal to the nozzle length, the average spacing between extensions will about equal the length of the extensions. Extensions of the type shown which extend outwardly for about 5 inches and are spaced on 5-inch centers are advantageously used. These extensions were 2 inches wide at the base and 1 inch deep which provided openings communicating with the associated nozzles to produce an adequate supply of air within the extensions.

It will be understood that various changes and modifications may be made in the above described construction which provide the characteristics of this invention without departing from the spirit thereof, particularly as defined in the following claims.

That which is claimed is:

1. In a web drier construction comprising a housing defining inlet and outlet openings and means for transporting a web through the housing, air nozzles positioned transverse to the direction of web movement, a conduit structure for feeding air to said nozzles for discharge through the nozzles into contact with the web, and an exhaust means connected to the housing for withdrawing air from within the housing, the improvement comprising nozzle extensions formed in the nozzles positioned adjacent the inlet and outlet openings and extending longitudinally of the web and at spaced intervals across the web, said nozzle extensions being positioned on the respective sides of the nozzles closest to said inlet and outlet openings, air discharge openings defined by said extensions defined to direct air onto said web and transversely across the web to thereby at least partially oppose the longitudinal air flow moving over the web surfaces toward said inlet and outlet openings.

2. A construction in accordance with claim 1 including a plurality of extensions located at spaced intervals along the length of said nozzles, and slots defined by each of the extensions for directing air onto the web form movement of the air transversely across the web.

3. A construction in accordance with claim 2 wherein said extensions comprise triangular shaped members, said slots extending in a triangular path around the periphery of the members.

4. A construction in accordance with claim 3 wherein said nozzles are of the type defining a pair of discharge slots extending in spaced-apart, side-by-side relationship along the length of said nozzles, said extensions having a length when measured in the direction of web movement exceeding the spacing between the slots in the nozzles whereby the slot length for each extension is at least two times greater than said spacing.

5. A construction in accordance with claim 1 wherein opposed sets of nozzles are provided for the discharge of air into contact with both surfaces of a web, the nozzles in one set being staggered relative to the nozzles of the other set, and wherein the extensions are associated with at least those noz- 

1. In a web drier construction comprising a housing defining inlet and outlet openings and means for transporting a web through the housing, air nozzles positioned transverse to the direction of web movement, a conduit structure for feeding air to said nozzles for discharge through the nozzles into contact with the web, and an exhaust means connected to the housing for withdrawing air from within the housing, the improvement comprising nozzle extensions formed in the nozzles positioned adjacent the inlet and outlet openings and extending longitudinally of the web and at spaced intervals across the web, said nozzle extensions being positioned on the respective sides of the nozzles closest to said inlet and outlet openings, air discharge openings defined by said extensions defined to direct air onto said web and transversely across the web to thereby at least partially oppose the longitudinal air flow moving over the web surfaces toward said inlet and outlet openings.
 2. A construction in accordance with claim 1 including a plurality of extensions located at spaced intervals along the length of said nozzles, and slots defined by each of the extensions for directing air onto the web form movement of the air transversely across the web.
 3. A construction in accordance with claim 2 wherein said extensions comprise triangular shaped members, said slots extending in a triangular path around the periphery of the members.
 4. A construction in accordance with claim 3 wherein said nozzles are of the type defining a pair of discharge slots extending in spaced-apart, side-by-side relationship along the length of said nozzles, said extensions having a length when measured in the direction of web movement exceeding the spacing between the slots in the nozzles whereby the slot length for each extension is at least two times greater than said spacing.
 5. A construction in accordance with claim 1 wherein opposed sets of nozzles are provided for the discharge of air into contact with both surfaces of a web, the nozzles in one set being staggered relative to the nozzles of the other set, and wherein the extensions are associated with at least those nozzles which are closest to the inlet and outlet openings of said housing.
 6. A construction in accordance with claim 5 wherein said extensions are associated with both end nozzles of each set.
 7. A construction in accordance with claim 1 including exhaust means positioned adjacent said inlet and outlet openings whereby air curtains are formed between these openings and the exhaust means, the ends of said extensions being located in spaced relationship relative to said openings whereby said air curtains will not be disrupted by the presence of said extensions. 